Onam is an annual Indian harvest festival celebrated by all people of Kerala irrespective of religion. A major annual event for Keralites, it is the official festival of the state and includes a spectrum of cultural events.
Onam commemorates Vamana and Mahabali. According to Hindu legends, Onam is celebrated in Kerala in memory of the governance under the rule of the mythical daitya king Mahabali who once ruled Kerala. Upon being visited by a dwarf Brahmana who requested three steps of land, Mahabali agreed; the visitor quickly grew in size and walked the entirety of the universe in the first two steps. Mahabali offered his own head for him to place a third step and was thus sent to the pātāla (netherworld), blessed for his piety to return to his earthly kingdom once a year.
Onam is celebrated according to the lunisolar Malayalam calendar, falling on the nakshatra Thiruvonam in the month of Chingam corresponding to August–September in the Gregorian calendar.